NEW YORK — The 40-year-old son of former ABC News anchor Ted Koppel was found dead in an apartment in upper Manhattan after a day of bar hopping with a man he met at a watering hole, a law enforcement official said Tuesday.

Andrew Koppel was declared dead around 1:30 a.m. Monday in the apartment in the Washington Heights neighborhood, Detective John Sweeney said. The cause of death has not been determined.

Koppel had been drinking heavily for hours with a man he met at a bar, according to a law enforcement official. The official spoke to The Associated Press on condition of anonymity because the investigation into the death was not completed.

Koppel started drinking at Smith's Bar and Restaurant in Manhattan and went to several other locations with the man, the official said.

Russell Wimberly told the New York Post he was drinking with Koppel all night.

"He had a straw hat on, and I had one on, and he said, 'Nice hat, man,'" the drinking partner, Wimberly, told the newspaper. "We got to talking, and he started buying me drinks."

Wimberly said that Koppel drank whiskey, and that neither man had anything to eat all day.

Koppel was appointed attorney for the city Housing Authority's civil litigation division in 2001, a post he resigned in 2008, the agency said Tuesday.

Ted Koppel was the longtime anchor of the ABC News show "Nightline." Andrew Koppel, of Queens, was one of his four children. A call to the elder Koppel's publicist was not immediately returned Tuesday.

Andrew Koppel was convicted of misdemeanor assault in 1994 for striking a U.S. Senate aide during an argument at a Capitol Hill automated teller machine. At the time, he was a student at Georgetown Law School.

The two eventually wound up at the apartment, which belonged a friend of the drinking buddy, the official said. They told Koppel to sleep it off and later found that he had gotten sick and appeared not to be breathing, Wimberly told the Post. The two said they called 911.

An autopsy was performed Monday but results were pending further study, including toxicology and tissue testing, said Ellen Borakove, a spokeswoman for the city medical examiner. Additional tests were needed to determine the manner and cause of death, Borakove said. They will take a few weeks to complete.